Having been an early adopter of 64-bit, I tended to get a little tired of those people who liked to tell that there's no real benefit to 64-bit and I might as well run a 32-bit distro on the machine anyway as it only makes a difference if one uses more that 4GB of ram.
So, I was rather interested in reading this article on the Phoronix website comparing 32-bit, 32-bit PAE and 64-bit kernels on a machine with only 4GB of ram.
As you can see, except for gaming, the benefits of using 64-bit are quite considerable.

Then again, some distros managed to provide 32 to 64 compatibility quite early on, so few if any problems resulted. I can only assume that those who have been tearing their hair out over 64-bit must either be using very specific software, or distros that didn't manage compatibility very well.

I've been using 64-bit since I got my first 64-bit capable processor (Intel Q6600) and have continued to install the 64-bit versions andeven my laptop has been running 64-bit since I first installed Linux when I bought it 15 months ago (Asus G1S). That's 4 releases of Ubuntu all functioning extremely well, with only minor hassles with Adobe Flash which the 64-bit alpha release has fixed without any problems. IIRC it just needed the Ubuntu Karmic Partner repository enabling.

I'd be really interested if they repeated the tests with openSUSE and Fedora. Just how much of an impact does each distro make on the kernel? Are there noticeable differences between nVidia and ATI graphics on the different distros?

I've been using 64-bit since I upgraded to Karmic. I've had no problems at all apart from with Flash as detailed below.

jamie_tickner wrote:I used to use 64bit but had trouble getting flash, skype and some other stuff to work properly so I went back to 32bit. Now my previous errors have been addressed so I am back to 64bit.

I still have problems with flash in 64 bit. I need to hold the middle mouse button down to click buttons in many flash objects, it's rather strange. Should be fixed with Flash 10.1 with a native 64 bit flash, though

Having finally managed to take a couple of blank CDs to work with me, I'm now running Salix in 64-bit. Very impressive. The 32-bit version was substantially faster than most other 32-bit distros, and the 64-bit flies compared to it. I've not seen any compatibility problems -so far, everything I've tried works.

The most impressive thing was compiling - I built Osmo under the 32-bit version, timed. I've just done the same under the 64-bit version - around 40 % faster. Generating the dep list (always a pain under the 32-bit version) was stunningly fast.